"Seasonal and Interannual Variations in Atmospheric Oxygen and
Implications for the Global Carbon Cycle," R.F. Keeling (NCAR, POB 3000,
Boulder CO 80307), S.R. Shertz, 723-727. Measurements using a new
interferometric technique show that the O2 content of air varies seasonally in
both the Northern and Southern Hemispheres, and is decreasing from year to year.
The seasonal variations provide a new basis for estimating global rates of
biological organic carbon production in the ocean, and the interannual decrease
constrains estimates of the rate of anthropogenic CO2 uptake by the oceans.

"Thermal Skin Effect of the Surface Ocean and Its Implications for CO2
Uptake," J.E. Robertson (Plymouth Marine Lab., Prospect Pl., West Hoe,
Plymouth PL1 3DH, UK), A.J. Watson, 738-740. The upper 1 mm or so of the oceans
represents a cool "skin," with a temperature gradient such that the
surface is generally cooler than the bulk mixed layer by about 0.3° C.
Accounting for this temperature difference results in a calculated increased
global uptake of about 0.7 Gt C yr-1, helping to bring into closer agreement the
oceanic CO2 uptake determined by different methods.

"Phytoplankton Productivity in the North Pacific Ocean since 1900 and
Implications for Absorption of Anthropogenic CO2," P.G. Falkowski
(Brookhaven Nat. Lab., Upton NY 11973), C. Wilson, 741-743. Increases in
phytoplankton biomass reported recently for the central North Pacific could be
important in the global carbon budget if they are widespread. However,
historical records of Secchi depth data show that any widespread increases are
too small to have a significant effect on the rise in atmospheric CO2.

Estimates using Holdridge Life-Zone Classification show an increase in the
area occupied by forests for all four scenarios. Terrestrial C storage increases
0.4-9.5% above estimates for present conditions, representing a potential
reduction of 4-85 ppm in elevated atmospheric CO2.

Atmospheric pCO2 was prescribed for the period 1750-1990 using the
combined Siple ice core and Mauna Loa records. For 1980-1989, the calculated
average flux of CO2 into the ocean, added to the observed atmospheric increase,
totals 5.1 Gt yr-1. This is comparable to the estimated fossil CO2 production,
implying that other sources and sinks (such as deforestation, enhanced growth of
land biota, and changes in the ocean C cycle) must be approximately in balance.

A study of C in the biomass, forest floor and mineral soil of Lake States
forests indicates that C storage can be influenced by forest management.
Patterns of C storage in these moist temperate ecosystems are not as strongly
influenced by climatic variables as in grasslands to the west.

Reviews the oceanic carbonate system, which has sparked renewed interest in
the context of increasing atmospheric CO2, and the accumulation and dissolution
of calcium carbonate in seafloor sediments of the major ocean basins. The
primary controls on the observed distribution patterns of calcium carbonate are
(in addition to depth) surface productivity, dissolution, and dilution by
noncarbonate and nonbiogenic sediment.